GTTF: always run perf tests serially

cc/test/run_all_perftests.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/test/cc_test_suite.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleMock(&argc, argv);
+  cc::CCTestSuite test_suite(argc, argv);
+
+  // Always run the perf tests serially, to avoid distorting
+  // perf measurements with randomness resulting from running
+  // in parallel.
+  return test_suite.Run();
+}